It is known that, to produce glass fiber insulating materials, glass or mineral wool felts may be sprayed with aqueous adhesives based on phenol-formaldehyde resins or urea-formaldehyde resins for the purposes of consolidation. Adhesives having very high water contents have to be used because the adhesive is applied to the still highly heated glass or mineral mass and thermal decomposition phenomena and observed with low water contents. The water applied is evaporated during subsequent hardening of the adhesives and is let off as waste air.
It is not possible to prevent parts of the adhesive components from being lost together with the waste air. This is an economic disadvantage because this part of the adhesive is lost during formation of the bond. Above all, however, this process is attended by significant disadvantages when physiologically harmful, readily volatile components are given off with the waste air, as in the case of formaldehyde-containing adhesives, for example.
Accordingly, it is extremely desirable both for economic and for ecological reasons to reduce the proportion of readily volatile adhesive components in the waste air without at the same time losing the desirable properties of the adhesives.
This problem is solved by the present invention.